LOS ANGELES, July 28 -- Los Angeles Police have arrested two men and two juveniles in connection with the murder of a 24-year-old Chinese graduate student.

Jonathan DelCarmen, 19, and Andrew Garcia, 18, along with a 17-year-old boy and a 16-year-old girl, are suspected of robbing and beating University of Southern California (USC) student Xinran Ji around 12:45 a.m.(0945 GMT) Thursday near 29th Street and Orchard Avenue.

DelCarmen was booked on suspicion of murder, while the other three suspects were booked on suspicion of murder, assault with a deadly weapon and robbery.

Ji, an electrical engineering graduate student, was attacked while walking home and was found dead in his apartment hours later. A trail of blood marked the path Ji walked.

Investigators believe that after attacking Ji, the group went to Dockweiler Beach and committed another robbery in that area, where DelCarmen and Garcia were arrested Thursday, Andrew Smith of Los Angeles Police Department said.

The university has increased security around campus since two students were shot dead in April 2012, with two security personnel on each block. Both the 29th and 30th street are in the security area.

However, during the summer when many students are away, the number of security personnel is reduced and some USC students stated that they had not seen any on 30th street recently.

Smith said the department was doing "everything we can to ensure that things are safe for students at USC and to try and prevent any incident like this from ever happening again."

The Chinese Consulate General in Los Angeles Friday condemned the killing, warning other Chinese students to be more alert and take steps to protect themselves.